Hydraulic-machine arrangement with a plurality of machine units

ABSTRACT

A HYDRAULIC-MACHINE ARRANGEMENT FOR TWO OR MORE HYDRAULIC UNITS (E.G. PUMPS OR MOTORS) WHEREIN AT LEAST TWO SUCH UNITS ARE MOUNTED IN A COMMON SWINGABLE FRAME SUCH THAT THE FRAME, UPON ANGULAR DISPLACEMENT ABOUT ITS AXIS, ANGULARLY SHIFTS THE CYLINDER DRUMS OF THE AXIAL PISTON PUMP OR MOTOR FROM ITS NULL POSITION TO AN OPERATIVE POSITION, THE PIVOTAL FRAME HAS HOLLOW PIVOT PINS THROUGH WHICH FLUID COMMUNICATION WITH THE RESPECTIVE AXIAL PISTON MACHINES IS ESTABLISHED.

United States Patent Inventor Dietrich Kratzenberg Hirtcnborn, GermanyAppl. No. 818,502 Filed Apr. 23, 1969 Patented June 28, 1971 PriorityApr. 24, 1969 Germany P 17 03 260.9

HYDRAULIC MACHINE ARRANGEMENT WITH A PLURALITY OF MACHINE UNITS 3Claims, 8 Drawing Figs.

US. Cl 91/505, 417/269 Int. Cl F011) 3/00, F01b 13/04 FieldofSearch103/162,

[561 References Cited UNITED STATES PATENTS 2,931,250 4/1960 Ebert 74/687 2,987,006 6/1961 Bowers et a1. 103/1628 3,052,098 9/1962 Ebert 91/1753,137,243 6/1964 Beck et a1. 103/1628 3,148,628 9/1964 Boydell 91/506Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. GluckAttorney-Karl F. Ross ABSTRACT: A hydraulic-machine arrangement for twoor more hydraulic units (e.g. pumps or motors) wherein at least two suchunits are mounted in a common swingable frame such that the frame, uponangular displacement about its axis, angularly shifts the cylinder drumsof the axial piston pump or motor from its null position to an operativeposition; the pivotal frame has hollow pivot pins through which fluidcommunication with the respective axial piston machines is established.

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0 (Ross Attorney HYDRAULIC MACHINE ARRANGEMENT WITH A PLURALI'IY OFMACHINE UNITS My present invention relates to an axial-piston-machinearrangement having at least two axial-piston working units and, moreparticularly, to a hydraulic-pump or hydraulic-motor arrangement inwhich the capacity of the pump of motor units is controlled by tiltingone member of each unit relative to another about a pivot axis.

In the commonly assigned U.S. Pat. No. 3,4l0,220, entitled "Axial-PistonMachines" of myself and others, the commonly assigned copendingapplications Ser. No. 708,039 and 744,489 of 25 Feb. 1968 and 12 JulyI968 (now US. Pat. No. 3,495,542 as well as the applications and patentsmentioned therein, there are described axial-piston machines whichfunction as pumps or motors and which are of variable capacity.

In such systems, a rotating member may carry a plurality of angularlyspaced pistons which are reciprocated in dependence upon the position ofa drive flange or a "swashplate" may be rotated to axially reciprocatethe pistons in a so-called axial-piston pump in which the pistons lieparallel to the axis of a cylinder block.

The capacity of the pump is varied by adjusting the angle with which thedrive flange intersects the axis of the cylinder drum, since the strokeof the individual pistons depends upon this angle. ln avariable-capacity axial-piston motor, hydraulic fluid is fed to thecylinders and reciprocates the axial pistons to drive the shaft, againvia a plate upon which the pistons act and which may be inclined to theaxis of the cylinder drum or block with varying degrees of tilt. Theaxial-piston pump and axial-piston motor are generally described asaxial-piston machines and when two or more such machines are coupledtogether, they shall be referred to as axial-piston working units.

It has been proposed (see British Pat. specification 992,334) to coupletwo similar-type units together for joint operation and control. Systemsin which the coupled units are both either axial-piston pumps oraxial-piston motors, have the advantage that the total output may betwice that of a single unit and the efl'iciency of the hydraulic systemis increased. For other arrangements, each of the pumps of the coupledsystem may operate an independent load via a respective hydraulicnetwork.

It has been recognized in this connection that two relativelylow-capacity units operate at greater cost efficiency than a singleworking unit with the same total capacity.

For the most part, prior art systems recognizing the aforementionedadvantage, have provided each of the working units with a respectiveswingable housing, the housings of the two units being coupled togetherby a link bar, so that a single control unit, e.g. a fluid-operatedservocontrol motor, can shift them jointly. The systems for supplyingfluid to the units and carrying away the fluid output are relativelycomplex and inconvenient. Moreover, the use of several housings andtheir associated pivots etc. increases the spatial requirements of theunits and their cost.

It is, therefore, the principle object of the present invention toprovide a hydraulic system with two or more axial-piston working unitswhich will have the above-described advantages and yet will have fewerparts, be of lower cost and require less space than heretofore.

This object and others which will become apparent hereinafter, accordingto the present invention, are attained by providing a common swingableframe or housing, preferably in the form of an elongated trough in whichthe cylinder drums of two or more working units are mounted side by sidewith their axes in a common plane, and a pair of pivots swingablymounting the frame in a surrounding housing for pivotal movement aboutan axis perpendicular to the axes of the unit but coplanar therewith.

The pivots which should lie close to the point at which the cylinderdrums must tilt with respect to the drive flange or plate, areconstituted as tubular members serving as fluid ports which communicatewith the cylinder drums via passages formed in the swingable frame.Since only two pivots in axial alignment with one another are requiredfor each frame and each frame receives a number of hydraulic workingunits, only two pivots are required in place of the pivot pair for eachunit, and the units can be located closer together than in earliersystems.

According to another feature of this invention two such working unitsare provided in the swingable frame, one unit being proximal to each ofthe pivots and having its fluid passages connected to the tubular pivot,thereby defining independent fluid streams for the units, each of whichterminates in a port formed by the pivots. Moreover, the outer housingmay form a reservoir communicating via apertures in the swingablehousing or frame with the other side of each of the axial-piston units,thereby greatly simplifying fluid connection to the units.

. According to still another feature of this invention, the floor orbase of the trough-shaped swingable frame which is remote from thesingle-pivot axis thereof as noted earlier, is provided withkidney-shaped control and distribution ports, e.g. via afluid-distribution or valve plate positioned on the base of the trough,upon which the cylindrical cylinder drums may rotate to bring therespective axial-piston cylinders into registry with the kidney-shapedinlet port and the kidney-shaped outlet port in alternating succession.

The kidney-shaped inlet and outlet ports will be low-pressure andhigh-pressure ports, respectively, when the hydraulic unit is operatingas a pump and high-pressure and low-pressure ports respectively, whenthe units operate as motors. In either case, the low-pressure portscommunicate through the swingable frame or housing, with the interior ofthe outer casing which constitutes a reservoir. The high-pressurekidneyshaped ports in the control plate or base of the swingable framecommunicate via respective passages in the latter, with the ports formedby the tubular pivots.

The drive flanges of the hydraulic units are connected by gear means toa common shaft journaled in the outer housing opposite the controlled orvalve plate, the axial pistons of the units bearing upon these driveflanges.

v'hCfl one of the shafts of a drive flange extends out of the housingand the drive flange of the other unit is coupled thereto by directgearing, i.e. two gears in mesh with one another interconnect the shaft,the cylinder drums and shafts of the unit will rotate in opposite sense.When the units are to function identically, therefore, the kidney-shapedports, with respect to their function, must be connected inmirror-symmetrical relationship, i.e. the mutually outermost ports ofthe two units must have the same function and the mutually innermostports the same function. When the device is a pump, the outermostkidney-shaped ports of the control plane or base of the swingable framewill function as the high-pressure outlet while the innermost orcentrally located portion will constitute intakes for drawing fluid intothe cylinder drums.

According to another feature of this invention, the device is providedwith rotary slide valves or distributors which'are connected to thekidney-shaped ports so that the total output of the assembly (totalinput when the device is a hydraulic motor) will be coupled together sothat the capacity of the device is the sum of the capacities of theseveral units. Each of the kidney-shaped ports of each of the workingunits may be provided with a respective rotary slide valve so that theports may be reversible in function. Furthermore, in this arrangementand/or in an arrangement in which further working units are provided ineach swingable frame, the tubular pivots may be provided with aplurality of coaxial tubes defining respective ducts communicating withthe respective hydraulic units.

Moreover, the passages of the frame may be cast in situ or may be buildup by plates or the like which also serve as reinforcements for theswingable frame. Alternatively or in addition, the ducts may includetelescoping or flexible tubes to accommodate the swinging motion of theframe.

According to still another feature of this invention, two or moreswingable frames each having two or more hydraulic working units, arepivotally mounted in a common outer housing with their pivot axespreferably lying in a common plane and are interconnected with one ormore link bars so that the tilting movement of one swingable frame willalso tilt the other by the identical amount. The gear coupling of thehydraulic units is such that the units of each frame are coupledtogether by respective gears and possibly to the gears of the otherunits via an intermediary gear such that all of the units rotate in thesame sense and a single output shaft is provided for all of them.

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in which:

FIG. 1 is a cross-sectional view taken along an axial plane in adouble-pump arrangement according to this invention;

FIG. 2 is a cross-sectional view taken transversely to FIG. I;

FIG. 2A is a cross-sectional view taken along the line IIA-IIA of FIG.1;

FIG. 3 is a cross-sectional view, partly in elevation, through afour-unit apparatus according to this invention, the swivelable housingsbeing seen from behind;

FIG. 4 is an axial section through the device of FIG. 3 showing analternative position of the swingable housing in dotdash lines;

FIG. 5 is a diagram illustrating a feature of the invention;

FIG. 6 is a diagrammatic view, partially in cross section, showing analternative valve arrangement; and

FIG. 7 is an elevational view, partly broken away, illustrating furtherfeatures of the invention.

In FIGS. 1, 2 and 2A, l have shown a double-pump arrangement which, ofcourse, can also be used as a double-hydraulic motor as may be required.The outer housing or casing I, which is shown for convenience to be ofone piece but will generally have a removable cover plate or be boltedtogether from two housing halves, rotatably receives the drive shaft 2upon which a driving pinion 3 is mounted.

Pinion 3 meshes with the driven gear 4 of a stub shaft 5 also journaledin the housing for rotation about an axis parallel to the axis of shaft2 and coplanar therewith, the rotational plane being represented at P inFIGS. 2 and 2A and running parallel to the paper in FIG. I. The shafts 2and 5 each carry a drive or control flange 6 and 6', respectively, of apair of hydraulic pumps which will be described in greater detailhereinafler and may be constituted as described in the commonly assignedpatent or copending applications mentioned above.

Both of the pumping units are received in a pivotal or swingable frameor housing 9 which is elongated as shown in FIG. 2A and is provided atits open side (to the right in FIG. I) with a pair of laterallyprojecting hollow pivot pins 7 and 8 received in respective ballbearings 7' and d which, in turn, are lodged in recesses 7" and 8" ofthe housing 1 so as to allow the housing 9 to pivot about an axis Aperpendicular to the axis of the shafts 2 and 5 and lying in the plane Pin all operative positions of the frame 9.

The housing 9 is formed with a compartment 9' having a base 90substantially coextensive with the open mouth of this housing. A pair ofstationary axles l0 and 10' extend perpendicularly from the base 9a intothe chamber 9' and are locked to the swingable housing by lock washers10d, 10d and nuts 10b, 10b.

The axles l0 and 10' serve to retain the drums cylinders of the axialpiston pumps rotatable against the control or valve plate relative towhich they are rotatable, as described in the patent and copendingapplications mentioned above. Between the heads 10c and 100' of theseaxes and the forward faces 11' and 12 of the rotatable cylinder blocks,I may pro vide bearing means to facilitate rotation of the drums I1 and12 and take up the axial thrust as provided in these copendingapplications, while fluid-responsive means may be provided along theaxles l0 and 10', via respective shoulders to draw the head 10c and thehead 10c axially to the left as described.

The cylinder blocks II and I2 each have a rear face II", I2" slidablybearing against the control plate I5 which is formed with a pair ofkidney-shaped openings 15a, 15a serving as inlet ports for the hydraulicfluid to be pumped, and a pair of kidney-shaped openings 15b, 15bconstituting outlet ports of the respective pump units. Needle bearings10a, 10a, received in cylindrical cavities Ila 12a of the cylinderblocks 11, I2 rotatably mount the latter onto the axles I0 and 10'.

The cylinder blocks II and I2 are also formed with angularly equispacedcylinder bores 13, 13a adapted to communicate alternately with the ports15a, 15b, and 15a, 15b of the respective portion of the control plate 15as each cylinder block is rotated by the shaft 2 or 5, respectively.

Respective axial pistons I3, 13a are axially shiftable in the bores I3,13a to displace hydraulic fluid during the pressure stroke (to the leftin FIG. I) and to draw hydraulic fluid into the respective cylinder onthe intake stroke (to the right in FIG. I). Swivel rods I4, whoseball-shaped heads 14a are received in correspondingly shaped recesses 60of the drive flange 6 or 6', couple the pistons I3 and 13a with thesedrive flanges to reciprocate the pistons.

The common pivotal frame or support for the pump units, which aremirror-symmetrical about a median plane M of the device (FIG. I), isprovided with a pair of connecting lugs 16 which is linked to the rod 17of a servocontrol piston 18 responsive to fluid pressure to swing theframe 9 about the axis A (clockwise in FIG. 2) to shift the pumparrangement out of its null position in which it is shown in thedrawing.

At the opposite axial ends of the swingable frame 9, I providerespective fluid passages 19 and 19' which terminate at ports 19a and190 along the base and register with the outlet ports 15!: and 15b ofthe control plate IS. The pins 7 and 8 are, as previously noted, tubularand formed with passages 7a, 8a communicating respectively with passagesI9 and I9 to deliver fluid to the high-pressure outlet ports 21 formedat the bearings 7 and 8' in the housing I. In other words, bothkidney-shaped outlet ports 15b and 15b lie symmetrically at outerregions of the housing 9 and are connected with outlet ports of thehousing at the pivot axis A. The inlet ports 15a and I50 communicate viarespective bores 20 and 20' in the base 9a, opening into the interior Iaof the housing I which constitutes a reservoir supplying hydraulic fluidto the pumping units. An inlet port 22 delivers the hydraulic fluid tothe interior la of the housing.

When the shaft 2 is driven by a motor (e.g. an electric motor or a primemover), the gears 3 and 4, which are fixed to the shafts 2 and 5 insurethat both drive flanges 6 and 6' will be rotated in opposite senses withidentical angular velocities, thereby setting the cylinder drums 11 andI2 into rotation about their axles I0 and 10' in opposite senses.

When the pivotal frame 9 is swung by the servo piston 18, which ishydraulically displaceable in its cylinder lb integral with the housing1, the drums II and 12 are brought into positions in which the axes(e.g. the axis D shown in FIG. 2) no longer are aligned with the axis ofthe respective shaft and perpendicular to the respective drive flange 6or 6', but are inclined to the latter as represented, for example, bythe angle a in FIG. 2.

The drums II and I2 are thus swung out of their "null" position in whichthe volume of the cylinders I3 and I3a sweeping pass the input portsI5a, 15a, is equal to the volume as these cylinder bores sweep pass theoutput ports 15b and 15b. Under the "null" condition, there is no changein the effective volume of the cylinders and the pistons do not shiftthrough any stroke relative to the cylinder blocks.

In the upwardly swung position of the frame 9 (as seen in FIG. 2), thepistons are drawn in and out by the drive flange 6 or 6' as the drum isrotated to draw hydraulic fluid from the housing chamber 10 and throughthe passages 20 and 20' and then via the kidney-shaped inlet ports 15aand 15a into the cylinders 13 and 130. As the drums sweep around so thattheir cylinders are successively aligned with the output ports, thepistons are driven inwardly to displace the fluid via the outlet portsb, 15b, the passages 19 and 19 and the ports 21 to the load. Bothoutlets 21 are independent one from the other and can be connected viasuitable valves to deliver corresponding quantities of fluid to a commonline or to individual lines. Additional fluid is returned to the housingvia fitting 22.

It will be apparent that the frame arrangement 9 always allows bothpumps to be swung identically. It has been found, moreover, that it isadvantageous to provide means for controlling the servomotor 17, 18 in afeedback path, in accordance with the pressure developed by both of thepumping units. As shown in FIG. 5, the housing I has its shaft 2 drivenby the electric motor 40 while the output ports 21 each deliver fluidvia lines 41 and 42 to respective loads 43 and 44 in one position of thecorresponding distributing valve 45, 46. In another position, the valves45 and 46 may deliver the combined output of the two pumps to a commonload 47. The valves may be provided in the frame 9 to selectivelyconnect the ports of the units with pivot tubes together or undividedlyas desired.

The hydraulic return from the loads proceeds via line 48 to the inletfitting 22. In each of the lines 41, 42, there is a pressure-sensingelement 49, 50, the combined output of which operates a control 51, forthe servomotor 17, 18.

In the embodiment illustrated in FIGS. 3 and 4, two swingable flanges109 and 209 are provided and are pivoted one above the other at axes Aand A" defined by the fittings 121, 121' and 221, 221" constitutingoutlets for the fluid as previously described. The housing 27 carries abearing 270 (FIG. 4) in which the drive shaft 25 is journaled. Thisdrive shaft can be tied to the usual electric motor by any conventionalmeans. Within the housing 27, the drive shaft 25 carries a pinion 24which meshes with the four gears I03, 203 and 104, 204 which are pairedas described in connection with FIGS. 1 and 2 to operate the pump unitsof each frame. The device of FIGS. 3 and 4 thus has four pump units eachhaving a kidneyshaped hydraulic inlet port 120, I and 220, 220communicating via the respective control plate 115, 215 with thecylinder drums as represented at 111 and2l1 in FIG. 4. It will beunderstood that a second cylinder drum, corresponding to the drum 12, isprovided in each of the frames 109, 209 but is not visible in FIG. 4. Aservomotor including a cylinder 27b, a piston 18, a piston rod 17 and apair of lugs 16, pivotally connecting the piston rod 17 to the lowerframe 209 serves to angularly shift the frames between the null positionof the device represented in solid lines in FIG. 4 and the maximum pivotposition shown in dot-dash lines, in which the pumps operate at maximumcapacity. The single inlet 22 delivers hydraulic fluid to the interior27c of the housing 27 from which rotation of the cylinder drums 111,211, etc. draws the fluid into the cylinders 113,213 in which the axialpistons 113', 213 are axially shiftable by the respective controlflanges 106, 206 as the drums III, 211 are rotated about the axles 110,210.

The drive flange 106 of the upper pair of pumps (FIG. 3) have respectiveshafts 23 carrying the gears 103, 104 in mesh with a common gear 24 sothat both drums of each pair and all four of the cylinder drums arerotated in the same sense.

As shown in FIG. 5, all four outlets 21 can be connected via respectivevalves or distributing arrangements so that both outlets of each framemay be connected together to a common load, all four outlets may be tiedto the common load, or each outlet 121, 121', 221, 221' have beenconnected to an individual load. When the outlets are doubled to oneload, the quantity of fluid displaced is double and the four-pumparrangement of FIGS. 3 and 4 act as a double-pump arrangement. Since theoutlets may be tied together in any combination or used individually,this system may constitute effectively a triple or quadruple pumpsystem.

As in the embodiment of FIGS. 1, 2 and 2a, the servomotor acts upon thehousing at a location remote from its pivot axis A, A" whichsubstantially lies in the plane of the drive flanges. In the embodimentsof FIGS. 3 and 4, the lower frame 209 is connected to the upper frame109 via a rigid link 26 and pivots 26' and 26" thereof.

It is self-understood that while the illustrated embodimentinterconnects the two swingable frames for joint and equal pivotaldisplacement, it is possible to provide means for shifting these framesindividually (i.e. a respective servomotor I6- l8, etc.) or to couplethe frames with a linkage maintaining a predetermined relationship inthe pivotal movements of one frame with respect to the other. When theframes are provided individually with servomotor means, I prefer to havethem swing outwardly from one another as they move out of their nullposition, whereupon the symmetrical configuration of the housing is alsorequired. Should it be desired to rotate the pumps in opposite senses asin the systems of FIGS. 1 and 2, the central pinion 24 can be dispensedwith and the gears of the individual pumps meshed in a chain so that oneof the pump shafts can be driven to operate all of the pumps. A chainarrangement of this type, however, depends upon exactitude in providingthe teeth of the gears if the output of each pump is to equal that ofthe others. Of course, the pinion 24 can also be shifted from one sideto mesh, for example, with both the gears 103, 203. In this case, gears103 and 104 and gears 203, 204 may interrnesh and the chain avoidedwhile the units of each frame are driven in opposite senses.

In FIG. 6, I show diagrammatically how the ports 60 and 61 of a controlor valve plate 62 within a swingable frame are connected to respectiveducts formed as coaxial tubes 63 and 64 in a hollow pivot of the typeshown at 7, 8 and 21 in FIG. I. These ducts are tied to a rotary slidevalve 65 of the distributing type, each of the hydraulic units beingprovided with such a valve as described in connection with FIG. 5. Therotary slide valve 65 is hydraulically connected to the hydraulic motor66 which mechanically operates a load 67 and to a reservoir 68, whichcan be the outer casing of the machine. Using the rotary slide valve 65,the functions of the ports 60 and 61 can be interchanged and reverserotation of the cylinder drum accommodated.

In FIG. 7, I show an arrangement where, unlike FIGS. 1 and 2A in whichthe ducts in the swinging frame 9 are cast in situ, the ducts 70 arebuilt up by bolting plates 71 and 72, 73 and 74 together to form theswinging frame, a pivot of which is shown at 75. Similar plates form thebase of the trough of the swingable frame which receives the control ofvalve plate 76. Unused ducts can be closed by plugs 77, while theflexible tubes 78 with telescoping tube portions 79 can be used toconnect the ducts 70 etc. with the load etc. When it is desired to avoidthe use of rotating ducting arrangements.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art. all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

I claim:

I. A hydraulic installation comprising:

a housing;

a trough-shaped support received in said housing and having a generallyflat bottom and a pair ofoutwardly turned pivot members at opposite endsof support defining a pivot axis parallel to said bottom, said bottomdefining a pair of fluid-distribution surfaces each surrounding arespective rotation axis coplanar with said pivot axis but perpendicularthereto and spaced apart along the pivot axis, each of said surfaceshaving a pair of diametrically opposite arcuate ports centered on therespective rotation axis, said ports including inner ports relativelyproximal to one another and outer ports relatively distal to oneanother, said trough-shaped support being provided with a pair ofpassages each connecting one of said outer ports with a respective oneof said members for conducting fluid therethrough and at least onefurther passage communicating between said proximal ports at theinterior of said housing around said trough-shaped support, said housingforming a pair of journals rotatably receiving said members whilepermitting fluid communication therethrough;

2. The hydraulic installation defined in claim I wherein two suchsupports are provided in said housing for swinging movement aboutrespective parallel pivot axes lying in a common plane, saidinstallations further comprising link means interconnecting saidsupports for joint swinging movement through identical angles.

3. The hydraulic installation defined in claim 2 wherein said gear meansincludes a respective driven gear fixed to each of the shafts of thecylinder barrels of each of said supports, and a common drive gearmeshing with all of said driven gears.

